John Seal

Finger Pairings in Two-Choice Reaction Time Tasks: Does the Between-Hands Advantage Reflect Response Preparation?

Two fractionated RT experiments tested whether the response-preparation or response-implementation hypothesis better accounts for the observation that two-choice reaction time (RT) usually takes longer when the responses are performed by the fingers of the same hand (within-hand repertoire) than by the fingers of the two hands (between-hands repertoire). In Experiment I (n equals 8), the effect of repertoire on the premotor time and the motor time were studied. RT was divided into the two periods with respect to the onset of change in electromyographic (EMG) activity of the flexor digitorum profundus. Type of repertoire affected both time periods. In Experiment 2 (n = 16), the effects of repertoire and foreperiod duration on the premotor and motor times of the flexor digitorum profundus and flexor digitorum sublimis were studied. The results of Experiment I were confirmed, and the effects of repertoire and foreperiod duration were found to be additive on premotor time but interactive on motor time. These findings led to rejection of the response-preparation hypothesis and instead supported the view that the central command for the flexion of the right middle finger differs according to the type of repertoire. The command appears to specify a lower rate of recruitment of the prime movers in the within-hand repertoire than in the between-hands repertoire. The execution of the central commands may depend on the state of excitability of the spinal neurons. Analysis of the EMG signals revealed that speed of contraction of the prime movers depends on repertoire when the foreperiod is long but not when it is short. The additivity of the effects of repertoire and of foreperiod duration on premotor time support the view that regardless of the state of preparation of the subject the pattern of EMG activity required for flexion of the right middle finger in each repertoire is specified during the premotor time.

A critical re-examination of the concept of function within the neocortex of the monkey

Abstract Combined neurophysiological/psychophysiological experiments have been applied to the study of how motor acts are planned. The justification for these experiments was the structural isomorphism between theoretical stage models of information processing and the supposed functional specialization of cortical areas. However, recent developments in both fields now suggest that the assumptions on which this isomorphism is based may be erroneous. Describing the results of our own combined experiments, we attempt to show how the concept of function within the cerebral cortex needs to be revised. We present new interpretations of data from single neuron recording experiments in three cortical areas which challenge the traditional idea of structure/function. In its place, we propose the hypothesis of a continuum of function going from sensory input to motor output.

Intensity to force translation: a new effect of stimulus-response compatibility revealed by analysis of response time and electromyographic activity of a prime mover

In reaction time studies of stimulus-response compatibility, emphasis has been placed on the influence of spatial stimulus-response relationships, but what seems to be essential for the emergence of an effect of stimulus-response compatibility is the existence of a conceptual match between stimulus and response variables. This notion was at the origin of the present study to assess the compatibility relationship between the intensity of a visual stimulus and the force of a voluntary muscle contraction. A stimulus-response compatibility effect was demonstrated. This effect was entirely due to premotoric processes.

Sensory Processing in the Mammalian Brain. Neural Substrates and Experimental Strategies: edited by Jennifer S. Lund, Oxford University Press, 1989. £36.00 (xii + 368 pages) ISBN 0 19 504554 8

No wonder you activities are, reading will be always needed. It is not only to fulfil the duties that you need to finish in deadline time. Reading will encourage your mind and thoughts. Of course, reading will greatly develop your experiences about everything. Reading sensory processing in the mammalian brain neural substrates and experimental strategies is also a way as one of the collective books that gives many advantages. The advantages are not only for you, but for the other peoples with those meaningful benefits.